This invention relates to infusion pumps. There are many applications for which there is a need for a device which can intravenously administer a plurality of drug solutions. One such application is the use of chemotherapy to treat such diseases as cancer. Attempts at providing more advanced chemotherapy regimens involving the intravenous administration of a multiplicity of drug solutions are being inhibited by a lack of equipment to simplify such a procedure. Very often if different drug solutions are used, they are administered by using a separate catheter tube for each drug. A separate infusion pump would be used on each individual catheter tube line and the tube would deliver the fluid solution into the patient through its respective intravascular access needle. A patient must pay for each catheter set and must rent a pump for use with the catheter tube. Therefore, it is costly to use multiple catheter tubes and pumps.
Some physicians administer chemotherapy treatments with a plurality of drug solutions by mixing the solutions together and feeding the mixture into the patient through a single catheter set and pump. If the different drug solutions are compatible they can be mixed and delivered through a single catheter. Unfortunately, there are only a limited number of drug combinations which can be used in this manner. Many drugs cannot be mixed together prior to infusion. Some drugs react to neutralize one another. Other drugs react to form precipitates which may block the catheter tube or possibly cause an embolism in the patient.
It is desirable to provide a single pump that can deliver a multiplicity of drug solutions without mixing any of them prior to infusion. It is especially desirable for the pump to be lightweight so that it might be used on an ambulatory patient. U.S. Pat. No. 4,313,439 (Babb et al.) recognized the need for lightweight infusion pumps in a single drug delivery system. Babb et al. provided an escapement mechanism which applied a continuous pressure to a syringe. A constrictor acted on a catheter tube to prevent fluid from passing through the tube except during periods when the force from the constrictor was released to allow fluid through the tube.